<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>destructuring</title>
</head>
<body>
<script>
    // 5、函数参数的默认值
   jQuery.ajax=function (url,{
       async=true,
       beforeSend=function () {},
       cache=true,
       complete=function () {},
       crossDomain=false,
       global=true
   }){}

   // 避免了函数体内  再写 var foo=config.foo或者 'default foo'
</script>
</body>
</html>